Repair r9 390 nitro gpu

[more_stars]

Hello guys,

My name is Alex and firstly I would like to say how much I will appreciate all the help and effort in diagnosing my problem.

I have a r9 390 nitro gpu that I bought as broken because I really wanted to upgrade my existing hd6850 gpu. I do repair some basic staff and troubleshoot tv's xbox controllers and power bricks but never attempting to repair a pcb with only smd s and so many components.

Firstly I plugged the card in my computer and checked what is doing. The gpu's bios switch powered on but that was it so I took the radiator off and plugged the gpu back in the motherboard. When powering the pc, the main gpu did not heat up so I tried to measure the voltages across the phases. I only came across the 12v inductor that is near the aux vrm but all the vrm's did not display any voltage what so ever. I tested the 3553m mosfet and they all seem to work fine but the 4c10n ware shorted on the drain and source so I tooked them out and I have seen that the mosfet are perfectly fine but the pads are still shorted. I checked with the ohm meter and there is an 0.1 ohm in there betueen D and S. The ohm reading from ground to the other phases are 2.2 ohm for the gpu vrm, 0.2 for aux vrm, 0.2 for mem vrm and 0.1 for 0.98v rail.

Also, I can't take the inductor off from the memory vrm to see if the short is from the memory chips or from the mosfet controller. I have seen some guys using ipa and applying a small voltage to see whether there is a component that is heating up but I don't know where to apply that power and I also don't want to destroy the whole card.

I also have another xfx rx 470 with 8gb that has two thick lines with green and pink throughout the screen. This was given to mt by a friend who used it in mining. Is there any hope for this card?

thank you in advance!
Stay safe!

[JKKDev]

You talk about plugging the GPU into the motherboard but you never mention the two 8 pin power connectors. Did you connect those as well? If so and none of the VRMs are getting the 12V rail I would check around the two power connectors for broken fuses, missing resistors (is this the card they did overclocking with by removing a resistor on the 12V input and shorting it out?),... It would be nice to get an image of the setup as well as the card itself and the top righr corner also.

Another advice. If this is the only way you can afford upgrading (no disrespect ment here), you shouldn't just plug known broken stuff into your only PC and hope it doesn't break you motherboard aswell. Maybe get a cheap setup for testing. It only needs PCIE support so any old 775 socket mb with core 2 duo or similar will do. And when you're certain it works at least hardware wise you can plug it into a better machine. Just my 2 cents.

[more_stars]

The first time I tested the video card, I dindn't plug the two 8 pin pci-e connectors as I was thinking it will work without those but after some research I did understand that the gpu needs power from all the places so I connected the pci-e connectors as well but still nothing. I see that there are 2 fuses and two 0 ohm resistors near the pci-e conectors and another 0ohm resistor near the bvi video connector.

Also, I was not thinking that this can cause anything to my computer as the worst I could think of is shorting my psu. Actually I have another motherboard laying around with 4gb ddr3 and I will use this one for further testings.

[more_stars]

Also the full card

[JKKDev]

Oh boy, you are missing 4 chunky components to the left of the power connectors. Check out Actually Hardcore Overclocking's video on the R9 390 Nitro. According to him, those are voltage regulators (4C10N ON Semiconductor) for VRAM *gulp*. Let's hope VRAMs didn't get zapped. This still doesn't explain why you don't have 12V on other voltage regulators tho. Did you check the fuses and 0 ohm resistors for continuity?

I would suggest you start by finding a high res image of both sides of the PCB and carefully check if there is anything else missing. I wouldn't be surprised if someone used it as a parts card (or you might be lucky and someone before you already found the issue in the missing parts and only removed those...).

From this point on I'll use the markings from the above video as descriptors. At this point, we are testing the power supply for the card so there's no need to plug the card into the PCI-E slot (I believe it doesn't use the slot voltage supply for any functionality to the right of the VRAM modules, but I might be wrong...).

1) You need to find out if the 12V rail is present at all the voltage regulators of the 6 phases of Vcore (this should be the case whenever the 8-pin plugs are connected) or there is continuity from the 8-pin plug to the VRMs. Each of the 8-pin plugs has 3 +12V rails which should go directly to the Vcore VRMs. If the voltage isn't present you need to check the fuses.
2) Find out if the VRMs (IR3550) are being supplied with a PWM signal by the 6+2 phase controller (IR3567B) as well as Vcc. If there is no Vcc there probably isn't a PWM signal either so we look into a logic voltage regulation part of the board under the 8-pin connectors. If there's no PWM signal but the Vcc is present we move to the phase controller. If the signal is present the core should be running (or at least have the voltage needed). You could check the voltage on the capacitors to the left of the Vcore VRMs.
3) Find the 5V and 3.3V supply. The VRMs use 5V and the phase controller uses 3.3V as Vcc so both should be present on caps around the corresponding chips. If one is missing find the voltage regulator for those and at that point, you've probably located the fault.

EDIT: I just noticed something isn't quite right with your C4139 (bottom left of the card next to the last VRAM chip)

[more_stars]

The four missing mosfets are because I desoldered them as I said in the initl post. The drain and source ware shorted so I figured that I might desolder those and see if the mosfets are OK or not and after checking, the mosfets are OK but the pads are shorted or they seem to be shorted as the rrzistancecis 0.1 ohm.

The cap at the bottom left is like that because I also desoldered it but not with the hot air station. I will resoldervit properly thus time.

The 0 ohm resistors and fuses are all OK.

I did purchased another broken r9 390 nitro with 30$ but it will arrive Thursday. This way, if they don't have the same problem, I will have another pcb with working parts to check from.

I do think that the problem is with the mosfet driver but I don't know how to test is as I don't have an oscilloscope at hand.

[JKKDev]

My bad, I completely forgot about the detailed part of your description :/ Did you check for the 5V and 3.3V supplies tho (point 3 of the above post)?

[more_stars]

Ohh I haven't seen the point on your reply. I will check them now and let you know.

Also, thank you very much for this help. I wrote to hardcore overclocking but he blocked me right away ) I think I was a bit to derailed on explaining.

[JKKDev]

Also if you check the IR3550 datasheet you can see a typical configuration for MOSFETs, coils, caps, etc. for the supply. The only way I could see the MOSFET pads being shorted was if one of the caps around them is bad or, the bad outcome, which is that the VRAMs are shorted. From your description of all the MOSFETs being shorted it, unfortunately, sounds like the latter.

Can you maybe figure out how the 2.2 ohm resistor under the coil is connected to the circuit? If it is inline you could desolder it to see which side is shorting.

In short, there should be two pairs of MOSFETs. Each pair should have one source on 12V rail, one drain on GND and one source and one drain connected together. Where the two connect the coil should also be connected as well as some capacitors.

[more_stars]

So, this is what I come across:
C658=1.7v
C650=3.2v
C714=0.3v
C4136=12v
C4118=12v
C4037=6v
C327=5v
C4034=12v
C4139=1.7v
C320=12v

At the 6 gpu phases the drain is not shorted with the source and the source have indeed 12v but I don't seem to have ir3550 but ir3553.

The mosfet from the memory VRM are the ones that have the source shorted to drain. Those mosfets are 4c10n.

I don't have an oscilloscope to check the pwm of the driver so is there any way to check the driver or I need to take it out fro the board and see if the shirt is still there. Also, I think that the ir3567b driver is only for the 6 phases for the gpu and I don't know where is the driver for the memory phase.

Also, the inductor is just too big to be desoldered with my basic soldering iron.

[JKKDev]

At this point you have all the power rails I would expect present so if there's nothing wrong with the PWM you should have output from the Vcore VRMs. I would check voltages on all 10 capacitors to the left of the coils (measure on the back of the PCB).

Also when I was talking about the structure of the two mosfet driving the phases I was talking about the VRAM VRMs and comparing them to the Vcore structure.

We should expect a similar structure and as the phase driver is a 6+2 I would expect the 4 VRAM mosfets to just be discreet versions of the Vcore VRM and function somewhat similarly.

Let's first figure out if Vcore is good and we'll take care of VRAMs after Too many different things to talk about at the same time.

[PKTKS]

That LEFT regulator  showing ZERO volts
is the  top primary issue

A know problem in these boards which
should be checked is U10 IC (PCI regulator)

U10 vary across boards usually you may
find those in pics.  Both should be checked
until working properly so VCore VRM will be next

[more_stars]

 After managing to de solder one inductor from the Vcore, I was able to see that the voltage got a bit higher from 0v to 0.22v

Also, after investigating the pcb I was unable to find the u10 ic. All I could find was u3, u4010, u1704, u350, u4017, u4018, u4, u2, u700, u201 and u1000.

Near the PCI are two big ic s apl5930 and 25l0010 be1611

[more_stars]

 I also took a photo at that side of the biard

[JKKDev]

That LEFT regulator  showing ZERO volts
is the  top primary issue

A know problem in these boards which
should be checked is U10 IC (PCI regulator)

U10 vary across boards usually you may
find those in pics.  Both should be checked
until working properly so VCore VRM will be next

Do you think (or know even) that the PWM is being suppressed/disabled because some of the PCIE side of things aren't working?

To the OP: Can you take a closer image of the left side of the pcb around where you measured 0V as well as one of just the board left of the VRAMs is visible?

[more_stars]

Also, the card is not recognised by the computer at all because with the card inserted, the computer boots up normally with the normal beep sound.

I also attached three more photos

[PKTKS]

Do you think (or know even) that the PWM is being suppressed/disabled because some of the PCIE side of things aren't working?

nah  no clue.

Usually I go every test possible out board to check
suspected too low impedance

But from the photo only? That zero regulator
may be preventing a dead shorted U10 to burn

Fairly common issue.
Unless the mosfets are already toasted

[more_stars]

I also have two of those rx470 8gb from xfx. One is only for parts and the other one have some artefacts but knowing that they ware used in mining, I thing that the problem is with some of the gddr5 memory chips.

If you think that I have more chances to repair this rx470 one, then, I will go with this one but also I would like to repair the r9 one as I already purchased another one for parts.

[JKKDev]

Ok, let's say the right side of the card is working (except the VRAM MOSFETs) and the PWM is being disabled/not enabled by the left side of the card.

At this point, I would suggest measuring the voltages on the three silver capacitors on the left side of the board. According to their rating, I'd expect 12V on the 16V one and 1.something V on the other two.

[more_stars]

On the 16v cap I can measure 12v but nothing on the other 3v caps.

[JKKDev]

On the 16v cap I can measure 12v but nothing on the other 3v caps.

Ok at this point just one image is missing. Could you post an image of the backside of the PCB around these caps? At this point, there is definitely a power supply problem somewhere on the card. We need to find which voltage regulator should be feeding the two caps that have no voltage on them. Please also measure if these two rails are shorted to ground (that would be another reason for 0V.

EDIT: NVM it's definitely the other IR3553 that is right there. Please look at the pinout of the IR3553 and confirm that it has 12V rail present on Vin, 5V Vcc present, and the SW isn't shorted to ground.

[more_stars]

 The rail is also shorted to the ground for those caps.

[JKKDev]

Any chance you could pull the coil and remeasure if the rails are still shorted?

Also the big chip (78M05G) you can see on the back is a 5V regulator supplying Vcc to the IR3553 it should have 12V on one side, ground in the middle and 5V on the other side of it.

[more_stars]

 The coil is just to big and I am afraid that if I put to much heat into the board, I will brake something. If you know haw to do it, tell me and I'm gonna try

[JKKDev]

The coil is just to big and I am afraid that if I put to much heat into the board, I will brake something. If you know haw to do it, tell me and I'm gonna try

It should be easy enough with a reasonably large tip. First, you need to add some new solder (preferably with Pb) to lower the melting point. Then you use the solder sucker to pull away as much of the solder as possible. If done properly you should be able to clean it enough to pull the coil off without using the iron in the end.

Also check the end of my previous post.